Have you ever felt bad when a friend did better than you? That feeling is envy. A Japanese research team looked at people's brains. When people read about someone better than them, a brain area linked to pain became active.

When something bad happened to that person, an area linked to rewards became active. But envy is not always bad. It can make you want to work harder, too.

Feeling a sting when a classmate gets top marks, or secret pleasure when a show-off fails, is very human. In 2009, a Japanese research team used brain scans to study these feelings. Nineteen participants read stories about imaginary classmates.

When a classmate was better than them in an area they cared about, participants felt strong envy, and a brain region linked to pain became active. When that classmate later suffered a misfortune, a region linked to reward became active. This pleasure at others' misfortune is called schadenfreude.

Psychologists also separate envy from jealousy. Envy involves two people and wanting what someone else has, while jealousy involves three people and the fear of losing a relationship. Dutch research also found that "benign envy" can motivate people to improve themselves.

A pang when a friend tops the class, a guilty flicker of satisfaction when a rival stumbles: both reactions are familiar, and a Japanese team traced them in the brain. In a 2009 study in Science, Hidehiko Takahashi and colleagues asked 19 participants to read profiles of fictional classmates during fMRI. When a classmate outperformed the participant in a personally important domain, reported envy was strong and the dorsal anterior cingulate cortex, a region linked to physical and social pain, became more active. When misfortune later struck that classmate, the striatum, part of the brain's reward circuitry, responded, and participants with stronger anterior cingulate responses showed a larger reward response.

The findings lend neural support to the proverb that others' misfortune tastes sweet, though the sample was small and inferring a specific feeling from activity in one region is risky. Psychologists also distinguish envy, which concerns two people and a desired advantage, from jealousy, which involves three people and a threatened relationship. Dutch researchers found that people experience benign envy, which motivates them to rise, differently from malicious envy, which makes them want to pull others down. Whether envy becomes fuel or poison may depend on whether success seems attainable.